Spain's solar sector flags record zero-price hours as investment risk

Spain has recorded roughly 900 hours of zero or negative solar power prices so far this year, industry group UNEF said, cautioning that sustained weak returns for producers could weigh on future investment even as the country's solar capacity keeps growing.

The figure already surpasses the 797 hours of zero or negative solar prices logged for the whole of last year, according to UNEF's 2025 report.

UNEF director general Jose Donoso described the price pattern in stark terms, saying it was "no longer a duck curve but the Mariana Trench" — a reference to the chart shape that shows solar prices typically dipping during peak generation hours and recovering as output falls.

Across Europe, the rapid build-out of solar capacity has widened the mismatch between supply and demand, producing more frequent stretches of zero or negative prices. Producers are increasingly left with a choice between paying to offload electricity or curtailing generation.

The pressure is visible in producer earnings. The average price earned by Spanish solar operators dropped to €29.68 ($34.24) per megawatt-hour in the first half of 2026, down from €36.39 per MWh across the whole of 2025 and €42.28 per MWh in 2024.

Capacity, meanwhile, continues to climb. Spain added almost 9 gigawatts of solar capacity last year, an increase of 31% over the previous year. New rooftop solar installations, however, slipped 4% from 2024 to about 1.1 GW, UNEF said.